OPTIONS

change the first configuration. This is the default and is
normally used for true OTP generation. In this configuration, the option
flag -oappend-cr is set by default.

-2

change the second configuration. This is for YubiKey II only
and is then normally used for static key generation. In this
configuration, the option flags -oappend-cr, -ostatic-ticket,
-ostrong-pw1, -ostrong-pw2 and -oman-update are set by default.

read configuration from file. (if file is -, read
from stdin) Configuration import is only valid for the ycfg format.

-fformat

format to be used with -s and -i. Valid options are ycfg and legacy.

-a[xxx]

the AES secret key as a 32 (or 40 for OATH-HOTP/HMAC CHAL-RESP) char hex value (not modhex) (none to prompt for key on stdin) If -a is not used a random key will be generated.

-c[xxx]

A 12 char hex value (not modhex) to use as access
code for programming. NOTE: this does NOT SET the access code, that’s
done with -oaccess=. If no argument is provided code is prompted for on stdin.

-ooption

change configuration option. Possible option arguments are:

fixed=fffffffffff

The modhex public identity of the YubiKey, 0-32 characters long
(encoding up to 16 bytes). It’s possible to give the identity in hex as
well, just prepend the value with ’h:’. The fixed part is emitted before
the OTP when the button on the YubiKey is pressed. It can be used as an
identifier for the user, for example.

uid[=uuuuuu]

The uid part of the generated OTP, also called private identity, in hex. Must be 12 characters long. The uid is 6 bytes of static data that is included (encrypted) in every OTP, and is used to validate that an OTP was in fact encrypted with the AES key shared between the YubiKey and the validation service. It cannot be used to identify the YubiKey as it is only readable to those that know the AES key. If no argument is provided the uid is prompted for on stdin.

access[=fffffffffff]

New hex access code to set. Must be 12 characters long. If an access code is set, it will be required for subsequent reprogramming of the YubiKey. If no argument is provided code is prompted for on stdin.

oath-imf=xxx

Set OATH Initial Moving Factor. This is the initial counter value for the YubiKey. This should be a value between 0 and 1048560, evenly dividable by 16.

ticket-flag

Set/clear ticket flag, see the section Ticket flags

configuration-flag

Set/clear ticket flag, see the section Configuration flags

-y

always commit without prompting

-d

dry-run, run without writing a YubiKey

-v

Be more verbose

-h

Help

-V

Version

YubiKey Neo only

-n URI

Program NFC NDEF URI

-t text

Program NFC NDEF text

YubiKey 3.0 and above

-m mode

set device configuration for the YubiKey. It is parsed in the form
mode:cr_timeout:autoeject_timeout
where mode is:

0

OTP device only.

1

CCID device only.

2

OTP/CCID composite device.

3

U2F device only.

4

OTP/U2F composite device.

5

U2F/CCID composite device.

6

OTP/U2F/CCID composite device.
Add 80 to set MODE_FLAG_EJECT, for example: 81
cr_timeout is the timeout in seconds for the YubiKey to wait on button
press for challenge response (default is 15)
autoeject_timeout is the timeout in seconds before the card is
automatically ejected in mode 81

Removing OTP mode also disable communication between ykpersonalize and
the YubiKey, further mode changes will have to be done with ykneomgr (for CCID mode)
or u2f-host (for U2F mode)

-S0605…

set the scanmap to be used with the YubiKey. It must be 45 unique
bytes as 90 characters. Leave argument empty to reset to the YubiKey’s
default. The scanmap must be sent in the order:

Note that you must remove any whitespace present in these examples before using the values.

YubiKey 2.3 and above

-u

Update existing configuration, rather than overwriting. Only
possible if the slot is configured as updatable.

-x

Swap configuration slot 1 and 2 inside the YubiKey. Only
possible if both slots are configured as updatable.

Ticket flags

tab-first

Send a tab character as the first character. This is usually used to
move to the next input field.

append-tab1

Send a tab character between the fixed part and the one-time password
part. This is useful if you have the fixed portion equal to the user
name and two input fields that you navigate between using tab.

append-tab2

Send a tab character as the last character.

append-delay1

add a half-second delay before sending the one-time password part. This
option is only valid for firmware 1.x and 2.x.

append-delay2

a half-second delay after sending the one-time password part. This
option is only valid for firmware 1.x and 2.x.

append-cr

a carriage return after sending the one-time password part.

YubiKey 2.0 firmware and above

protect-cfg2

When written to configuration 1, block later updates to configuration 2.
When written to configuration 2, prevent configuration 1 from having the lock bit set.

YubiKey 2.1 firmware and above

oath-hotp

Set OATH-HOTP mode rather than YubiKey mode. In this mode, the token
functions according to the OATH-HOTP standard.

YubiKey 2.2 firmware and above

chal-resp

Set challenge-response mode.

Configuration flags

send-ref

Send a reference string of all 16 modhex characters before the fixed part. When combined
with -ostrong-pw2 this sends a ! before the rest of the string.

pacing-10ms

Add a 10ms delay between key presses.

pacing-20ms

Add a 20ms delay between key presses.

static-ticket

Output a fixed string rather than a one-time password. The password is
still based on the AES key and should be hard to guess and impossible to
remember.

YubiKey 1.x firmware only

ticket-first

Send the one-time password rather than the fixed part first.

allow-hidtrig

Allow trigger through HID/keyboard by pressing caps-, num or scroll-lock
twice. Not recommended for security reasons.

YubiKey 2.0 firmware and above

short-ticket

Limit the length of the static string to max 16 digits. This flag only
makes sense with the -ostatic-ticket option. When -oshort-ticket is
used without -ostatic-ticket it will program the YubiKey in "scan-code
mode", in this mode the key sends the contents of fixed, uid and key as
raw keyboard scancodes. For example, by using the fixed string
h:8b080f0f122c9a12150f079e in this mode it will send Hello World! on
a qwerty keyboard. This mode sends raw scan codes, so output will differ
between keyboard layouts.

strong-pw1

Upper-case the two first letters of the output string. This is for
compatibility with legacy systems that enforce both uppercase and
lowercase characters in a password and does not add any security.

strong-pw2

Replace the first eight characters of the modhex alphabet with the
numbers 0 to 7. Like -ostrong-pw1, this is intended to support
legacy systems.

man-update

Enable user-initiated update of the static password. Only makes sense
with the -ostatic-ticket option. This is only valid for firmware 2.x.

YubiKey 2.1 firmware and above

oath-hotp8

When set, generate an 8-digit HOTP rather than a 6-digit one.

oath-fixed-modhex1

When set, the first byte of the fixed part is sent as modhex.

oath-fixed-modhex2

When set, the first two bytes of the fixed part is sent as modhex.

oath-fixed-modhex

When set, the fixed part is sent as modhex.

oath-id=m:OOTTUUUUUUUU

Configure OATH token id with a provided value. See description of this
option under the 2.2 section for details, but note that a YubiKey 2.1
key can’t report its serial number and thus a token identifier value
must be specified.

YubiKey 2.2 firmware and above

chal-yubico

Yubico OTP challenge-response mode.

chal-hmac

Generate HMAC-SHA1 challenge responses.

hmac-lt64

Calculate HMAC on less than 64 bytes input. Whatever is in the last byte
of the challenge is used as end of input marker (backtracking from end
of payload).

chal-btn-trig

The YubiKey will wait for the user to press the key (within 15 seconds)
before answering the challenge.

serial-btn-visible

The YubiKey will emit its serial number if the button is pressed during
power-up. This option is only valid for the 2.x firmware line.

serial-usb-visible

The YubiKey will indicate its serial number in the USB iSerial field.
This option is not available in the 3.0 and 3.1 firmwares.

serial-api-visible

The YubiKey will allow its serial number to be read using an API call.

oath-id[=m:OOTTUUUUUUUU]

Configure OATH token id with a provided value, or if used without a
value use the standard YubiKey token identifier.

The reason for the decimal serial number is to make it easy for humans
to correlate the serial number on the back of the YubiKey to an entry in
a list of associated tokens for example. Other encodings can be
accomplished using the appropriate oath-fixed-modhex options.

Note that the YubiKey must be programmed to allow reading its serial
number, otherwise automatic token id creation is not possible.

YubiKey 2.3 firmware and above

Send scancodes for numeric keypad keypresses when sending digits - helps
with some keyboard layouts. This option is only valid for the 2.x
firmware line.

fast-trig

Faster triggering when only configuration 1 is available. This option is
always in effect on firmware versions 3.0 and above.

allow-update

Allow updating (or swapping) of certain parameters in a configuration at
a later time.

dormant

Hides/unhides a configuration stored in a YubiKey.

YubiKey 2.4/3.1 firmware and above

led-inv

Inverts the behaviour of the led on the YubiKey.

OATH-HOTP Mode

When using OATH-HOTP mode, a HMAC key of 160 bits (20 bytes, 40 chars of
hex) can be supplied with -a.

Challenge-response Mode

In CHAL-RESP mode, the token will NOT generate any keypresses when the
button is pressed (although it is perfectly possible to have one slot
with a keypress-generating configuration, and the other in
challenge-response mode). Instead, a program capable of sending USB HID
feature reports to the token must be used to send it a challenge, and
read the response.

Modhex

Modhex is a way of writing hex digits where the “digits” are chosen for
being in the same place on most keyboard layouts.
To convert from hex to modhex, you can use: